In a communication system, information is transmitted via message signals through a physical medium from a source to a destination. For example, a cable-based system can be used to deliver high-definition digital entertainment and telecommunications such as video, voice, and high-speed Internet services from a headend to subscribers over an existing cable television network. The cable television network can take the form of an all-coax, all-fiber, or hybrid fiber/coax (HFC) network.
The message signals conveying the information to be transmitted can undergo modulation prior to transmission. Modulation generally is the process of converting the message signal into a form that can be transmitted over the physical medium. This can be achieved, for example, by superimposing the message signals on a carrier signal that is suitable for transmission over the physical medium. In a cable-based system, for example, digital bit streams representing various services (e.g., video, voice, and Internet) from various digital information sources are received at the headend where each digital bit stream is QAM modulated onto a respective carrier signal having a frequency that corresponds to a center frequency of a 6 MHz-wide RF channel to produce a single channel modulated RF carrier signal.
A plurality of single channel modulated carrier signals can be combined to produce a multi-channel signal. The multi-channel signal can be converted to an optical signal and transmitted downstream via a fiber to a fiber node that serves a group of end users (“service group”). The fiber node can include an optical receiver that converts the received optical signal to an electrical signal that then is transmitted to the service group, for example, via receiving devices such as cable modems (CMs) and/or settop boxes (STBs).
There is a growing demand for multi-channel modulators that can accommodate more channels; however, existing multi-channel modulators are computationally inefficient, among other limitations.